Python 如何在未执行的代码中查找异常？

在这个简单的Python代码中，如果

a

的值从

0

更改，则会出现

namererror

显示

b

未定义。但是，如果从未执行

else

子句，则错误将保持隐藏状态。如何检测此类错误

a=0
if a==0 :
  print "hello"
else :
  print b

能够在python代码中发现许多常见（但不太常见）错误，而无需执行，示例输出来自您的示例：

C:  1, 0: Exactly one space required around assignment
a=0
 ^ (bad-whitespace)
C:  2, 0: Exactly one space required around comparison
if a==0 :
    ^^ (bad-whitespace)
C:  2, 0: No space allowed before :
if a==0 :
        ^ (bad-whitespace)
C:  4, 0: No space allowed before :
else :
     ^ (bad-whitespace)
C:  1, 0: Missing module docstring (missing-docstring)
C:  1, 0: Invalid constant name "a" (invalid-name)
E:  5,10: Undefined variable 'b' (undefined-variable)

>>> a = 1
>>> if a == 0:
...     print a
... else:
...     try:
...         print b
...     except Exception as e:
...         print 'Caught Exception: ', e  # where e is the exception string
...
Caught Exception:  name 'b' is not defined

这里您感兴趣的一行是：

E:5,10:未定义变量'b'（未定义变量）

能够在python代码中找到许多常见（不太常见）错误，而无需执行它，示例输出如下：

C:  1, 0: Exactly one space required around assignment
a=0
 ^ (bad-whitespace)
C:  2, 0: Exactly one space required around comparison
if a==0 :
    ^^ (bad-whitespace)
C:  2, 0: No space allowed before :
if a==0 :
        ^ (bad-whitespace)
C:  4, 0: No space allowed before :
else :
     ^ (bad-whitespace)
C:  1, 0: Missing module docstring (missing-docstring)
C:  1, 0: Invalid constant name "a" (invalid-name)
E:  5,10: Undefined variable 'b' (undefined-variable)

>>> a = 1
>>> if a == 0:
...     print a
... else:
...     try:
...         print b
...     except Exception as e:
...         print 'Caught Exception: ', e  # where e is the exception string
...
Caught Exception:  name 'b' is not defined

---

您感兴趣的行是：

E:5,10:未定义变量“b”（未定义变量）

有两种方法可以实现这一点：

或者在块中包含这样的语句。例如：

C:  1, 0: Exactly one space required around assignment
a=0
 ^ (bad-whitespace)
C:  2, 0: Exactly one space required around comparison
if a==0 :
    ^^ (bad-whitespace)
C:  2, 0: No space allowed before :
if a==0 :
        ^ (bad-whitespace)
C:  4, 0: No space allowed before :
else :
     ^ (bad-whitespace)
C:  1, 0: Missing module docstring (missing-docstring)
C:  1, 0: Invalid constant name "a" (invalid-name)
E:  5,10: Undefined variable 'b' (undefined-variable)

>>> a = 1
>>> if a == 0:
...     print a
... else:
...     try:
...         print b
...     except Exception as e:
...         print 'Caught Exception: ', e  # where e is the exception string
...
Caught Exception:  name 'b' is not defined

使用还可用于获取与引发的

异常相关的所有信息

如果您希望在函数范围内执行此行为，请创建一个装饰器，并将该装饰器与需要此行为的函数一起使用

---

有两种方法可以实现这一点：

或者在块中包含这样的语句。例如：

C:  1, 0: Exactly one space required around assignment
a=0
 ^ (bad-whitespace)
C:  2, 0: Exactly one space required around comparison
if a==0 :
    ^^ (bad-whitespace)
C:  2, 0: No space allowed before :
if a==0 :
        ^ (bad-whitespace)
C:  4, 0: No space allowed before :
else :
     ^ (bad-whitespace)
C:  1, 0: Missing module docstring (missing-docstring)
C:  1, 0: Invalid constant name "a" (invalid-name)
E:  5,10: Undefined variable 'b' (undefined-variable)

>>> a = 1
>>> if a == 0:
...     print a
... else:
...     try:
...         print b
...     except Exception as e:
...         print 'Caught Exception: ', e  # where e is the exception string
...
Caught Exception:  name 'b' is not defined

使用还可用于获取与引发的

异常相关的所有信息

如果您希望在函数范围内执行此行为，请创建一个装饰器，并将该装饰器与需要此行为的函数一起使用

---

如果

a

定义为

a=0

（如OP示例所示），pylint将捕获此类错误创建a以抑制错误并打印/写入以记录异常，

else

子句将永远不会执行如果

a

定义为

a=0

（如OP示例中所示），则将永远不会执行

else

子句